There exist examples of electronic timing circuits producing a spark signal at a desired rotational angle of an internal combustion engine. For example, U.S. Pat. No. 4,066,968, Guipaud generates ramps and D.C. levels to produce time delays.
U.S. Pat. No. 4,035,619, Cholet shows a signal synthesizer which combines a rotational speed signal and an intake manifold pressure signal. An advance signal is generated responsive to these two input signals for a particular engine characteristic.
U.S. Pat. No. 4,063,538, Powell requires peak combustion chamber pressure be kept at a fixed angular position. Pressure is sensed in the combustion chamber and spark timing is varied to phase lock the position of the pressure peak to a fixed reference position.
U.S. Pat. No. 3,966,911, Canup uses a digital process to control the spark advance with an internal combustion engine.
While these patents contain examples of controlling the instant when a spark ignition signal is provided with reference to engine rotation angle and engine speed, they do not provide a system having a feedback arrangement to precisely control the period of a constant peak to peak amplitude timing signal corresponding to the engine speed.
These examples do not show, as a basic unit within the system, a cyclical signal generator producing a varying amplitude timing wave having a constant peak to peak amplitude and with its frequency and phase tied to a reference input signal through a phase-locked loop.
These examples also do not show the use of a saw-tooth constant peak to peak amplitude phase-locked loop generated signal, used to time an ignition system, where the saw-toothed timing signal period is tied to a reference signal corresponding to engine speed, and where the saw-tooth is used together with an engine spark advance curve signal, and wherein the ignition signal is triggered at a particular amplitude of the timing signal, corresponding to a particular amplitude of the engine spark advance curve signal, and corresponding to a predetermined angle of advance.
Additionally not shown is a means for changing the engine spark advance curve signal with regard to other engine conditions, such as engine vacuum, and for varying the level of the advance curve signal with respect to engine vacuum to change the engine rotational angle at which the spark signal is generated.